Ignition systems



1959 R. L. JAESCHKE 2,398,392

IGNITION SYSTEMS Fi led Aug. 19. 1957 FIGB. 7/

IGNITION SYSTEMS Ralph L. Jaeschke, Kenosha, Wis., assignor to EatonManufacturing Company, Cleveland, Ohio, a corporation .of OhioApplication August 19, 1957, Serial No. 678,952 I 8 Claims. (Cl. 123-149) This invention relates to ignition systems, and more: particularlyto transistorized automotive ignition systems.-

Amongtheseveral objects of the invention may be noted the provision ofignition systems which automati-;

cally and precisely control the advance and retardation of spark inresponse to engine speed variations; the provision of ignition systemsof the class described which insure improved flame propagation; and theprovision of such ignition systems which are simple and inexpensive in.

Fig. 1 is a schematic and circuit diagram ofan ignition' system of thepresent invention;

Fig. 2 illustrates the wave patterns at certain points in the ignitionsystem at low engine speeds; and,

. Fig. 3 illustrates the wave patterns at certain points in the ignitionsystem at higher engine speeds.

Corresponding reference characters indicate corresponding partsthroughout the several views of the draw- Referring now to Fig. 1, anautomotive type distributor is indicated at D. A distributor rotor DR isinterconnected by a wire 1 to a secondary TS of a step-up transformer T.Rotor DR is mechanically driven in the usual manner by aninternal-combustion engine (usually from the cam shaft), so as to sweepthe rotor across several distributor stator contacts D8 which are inturn electrically connected to the engine spark plugs as indicated.Transformer T, which is. preferably of the type used as the high voltagetransformer in conventional television sets, has a primary winding TP.The TPzTS turns ratio is such that a secondary voltage of approximately10 to kv. is developed. Transformer T may be of the laminated, air orcompacted powdered iron core types. One end of primary T P is commonlyconnected to the other side of secondary TS and grounded, while theopposite terminal of TP is connected through a resistor R1 to the base Bof a junction transistor JT. Primary TP is shunted by a condenser C1 toform an LC tank which resonates within a preferred frequency range ofabout 15 to kc. A tap of winding TP is connected to emitter E oftransistor IT. The basic oscillator circuitry of Fig. 1 also includes anadjustable bias resistor R2, interconnecting the collector element of ITto its base B, and a source of DC. power B1, such as a 12 v. automotivestorage battery interconnected through an ignition switch SW tocollector C.

This oscillator circuit, constituted by transistor JT connected in acommon-emitter configuration with its associated components includingthe LC tank and resistors R1 and R2, optionally but preferably alsoincludes a resistor R3 and a protective limiter diode D1 series- 10shunted across R1.

woundon two generator poles P1 and P2 magnetically;

connected between collector C and emitter E to protect:

In order to pulse or key this A.C. potential applied to DR, a pair ofserially connected generator windings GWl and GW2 are shunt-connected bymeans of a wire 3, a resistor R4, a wire 5, and another conductor 7across resistor R1. A diode limiter D2 is also electrically ThewindingsjGWl and GW2 are:

interconnected by the iron path providedby a generator stator elementGS.Aflux field through GS is estab-, lished by a polarized generator rotorGR positioned in a magnetic relationship between poles P1 and P2.. Thisrotor is of permanent magnetic material, such as Alnico,-

and is driven by the internal-combustion engine in a timed relationshiptherewith (half speed in the illustrated: embodiment). The rotation ofrotorGRvaries the flux cutting windings GWl and GW2, thus generating anA.C. signalvhaving a frequency and an amplitude which are functions ofengine speed, The .wave form of this; signal is preferably modified,-aswill be explained-m moredetail, hereinafterbythe R4 D 2 circuit andim,

. pressed across R1.--

j Operation is-as' follows:

Upon closing the ignition switch SW, the. D;C.' poi tential of batteryB1 is applied across the transistor base-f collector circuit, which'includes theLC tank circuit and R1 series-connected therewith. Theparameters of;

R1 and R2'(e.g., 1009 .and 200tl, respectively) arejsuch that a smallbiasing potential of about- 1 v. is developed; across base B-collectorC. by the voltage drop across R2.

'lhe generator G produces an.A.C'. Qsignal (across wires 3 and 7) havingthe wave shape X'-,('Fig.;2) or; some what truncated sine wave. Theactionof D2 "and R4, limit the negative excursions of this A G sigIiaI,cutting oif the dashed portion of-wave'X.

" The signal of a wave shape as "indicated by the solid line portions ofwave X causes a potential in accordance therewith to'be developed acrossresistor R1, which varying potential modifies the current through R2 andthus the potential between base B and collector C of transistor JT. At apredetermined point, referred to and illustrated as the trigger point(e.g., 3 v.), across wires 5 and 7, the net biasing potential becomessuch that transistor J T conducts heavily, initiating oscillation in theLC tank. This trigger point value may be varied as desired by adjustmentof rheostat R2. With a capacitance of about 50 to mfd, at C, the LC tankwill provide an A.C. signal at a frequency of about 15 kc., theamplitude of which is stepped up by the transformer action of T to apotential of about 10 to 15 kv. This oscillation, indicated by the waveform Y, continues until the amplitude of the generator signal decreasesand wave X becomes more positive than 3 v., the preselected triggerpoint. Thus, timed pulses of 15 kc. are produced, being initiated by theA.C. generator signal exceeding 3 v. in a negative direction and beingcut 01f by the signal falling back below this trigger point level. Theduration of this pulse is therefore controlled by the opertion ofgenerator G. At higher engine speeds, the frequency and amplitude of theA.C. generator signal are increased, as shown in Fig. 3. The wave formof the signal is illustrated at XI. The slope of the fiat wave sidesteepens at this higher speed, thereby intersecting the trigger level ata point earlier along the time base. This action inherently advances theinitiation of the 15 kc.

3 in that it prevents overdriving of transistor JT, which would causemodulation of the 15 kc. signal pulses at the rotational frequency ofrotor GR.

It is to be noted that the four pole rotor GR is rotated at one. halfthe engine speed, mat the same speed as the cam shaft. For six andeight'cylinder engines the rotor configuration orspeed is appropriatelymodified. Also, the wave form of the output of generator G maybemodified from that shown by changing the shape of the rotor and/orfaces of pole pieces P1 and P2. More than one spark pulse per cylinderexplosion may be obtained by providing several notches in the rotor,instead of providing continuous ignition over each burning cycle, as isthe case in the illustrated embodiment. Also, it is to be understoodthat junction transistors of the PNP as well as the NPN type may beused, if the customary In view of the above, it will be seen that theseveral objects of the invention are achieved and other advantageousresults attained.

- As various changes could be made in the above constructions withoutdeparting from the scope of the invention, it is intended that allmatter contained in the above description or shown in the accompanyingdrawings shall be interpreted as illustrative and not in a limitingsense.

I claim:

1. In an ignition system for an internal-combustion engine having aplurality of spark plugs and a distributor having a rotor driven by theengine, said distributor being electrically interconnected to saidplugsto supply sequentially thereto a series of timed high-voltagehigh-frequency electrical pulses; means for generating said series oftimed high-voltage pulses comprising an oscillator having an LC resonanttank circuit, a step-up transformer including at least a portion of theinductance of said tank circuit in the primary winding thereof andhaving a secondary winding electrically connected to said distributorrotor, said oscillator including a transistor and a biasing resistorresponsive to a voltage of predetermined amplitude to actuate saidoscillator, and a generator driven by said engine in timed relationtherewith, said generator being connected to vary the voltage acrosssaid biasing resistor and adapted to provide a series of shapedelectrical pulses having a wave form the amplitude and slope of theleading edge of which are functions of engine speed, whereby the time ofactuation of said oscillator is increasingly advanced as the enginespeed increases.

2. In an ignition system as set forth in claim 1, said generator havinga rotor and a stator, said rotor being of permanent magnetic materialand driven from a cam shaft of said engine, and said stator having poleswhich are shaped relative to the generator rotor to provide a generallytruncated sinusoidal wave form.

3. In an ignition system as set forth in claim 1, said biasing resistorbeing adjustable to vary the predetermined amplitude at which saidtransistor oscillator is actuated.

4. In an ignition system as set forth in claim 1, said transistor beingconnected in a common emitter configuration and having base, collectorand emitter electrodes, said biasing resistor being connected betweensaid base and collector, and said tank circuit being series connectedwith a source of DC. power between said base and collector.

5. In an ignition system as set forth in claim 4, a second resistorserially connected between said tank circuit and said transistor base,said generator being connected across said second resistor.

6. In an ignition system as set forth in claim 5, a diode limitershunted across said second resistor whereby excursions of one polarityof said electrical pulse wave form are clipped.

7. In an ignition system as set forth in claim 6, a second diode andresistor being serially connected between said collector and emitter.

8. In an ignition system as set forth in claim 7, said components ofsaid LC circuit having parameters which provide a resonant oscillatorfrequency of approximately 15 to 20 kc.

References Cited in the file of this patent UNITED STATES PATENTS2,490,960 Hanchett Dec. 13, 1949 2,536,143 Short Jan. 2, 1951 FOREIGNPATENTS 1,137,949 France Jan. 21, 1957 UNITED STATES PATENT OFFICECERTIFICATE OF CORRECTION Patent No., 2,8983%; August 4, 1959 Ralph LoJaeschlce It is herebfi certified that error appears in the -printedspecification of the above numbered patent requiring correction and thatthe said Letters K Patent should read as corrected below.

Oolumn 3, line 16, after "customary" insert M polarity reversals aremade, o

Signed and sealed this 12th day of January 1960.,

(SEAL) Attest:

KARL .AXLINE. ROBERT C. WATSON Attesting Officer Commissioner of Patents

